/*
 *   This program is free software: you can redistribute it and/or modify
 *   it under the terms of the GNU General Public License as published by
 *   the Free Software Foundation, either version 3 of the License, or
 *   (at your option) any later version.
 *
 *   This program is distributed in the hope that it will be useful,
 *   but WITHOUT ANY WARRANTY; without even the implied warranty of
 *   MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
 *   GNU General Public License for more details.
 *
 *   You should have received a copy of the GNU General Public License
 *   along with this program.  If not, see <http://www.gnu.org/licenses/>.
 */

/*
 *    PolyKernel.java
 *    Copyright (C) 1999-2012 University of Waikato, Hamilton, New Zealand
 *
 */

package weka.classifiers.functions.supportVector;

import java.util.Collections;
import java.util.Enumeration;
import java.util.Vector;

import weka.core.Capabilities;
import weka.core.Capabilities.Capability;
import weka.core.Instance;
import weka.core.Instances;
import weka.core.Option;
import weka.core.Utils;

/**
 * <!-- globalinfo-start --> The polynomial kernel : K(x, y) = &lt;x, y&gt;^p or
 * K(x, y) = (&lt;x, y&gt;+1)^p
 * <p/>
 * <!-- globalinfo-end -->
 * 
 * <!-- options-start --> Valid options are:
 * <p/>
 * 
 * <pre>
 * -D
 *  Enables debugging output (if available) to be printed.
 *  (default: off)
 * </pre>
 *
 * <pre>
 * -C &lt;num&gt;
 *  The size of the cache (a prime number), 0 for full cache and 
 *  -1 to turn it off.
 *  (default: 250007)
 * </pre>
 * 
 * <pre>
 * -E &lt;num&gt;
 *  The Exponent to use.
 *  (default: 1.0)
 * </pre>
 * 
 * <pre>
 * -L
 *  Use lower-order terms.
 *  (default: no)
 * </pre>
 * 
 * <!-- options-end -->
 * 
 * @author Eibe Frank (eibe@cs.waikato.ac.nz)
 * @author Shane Legg (shane@intelligenesis.net) (sparse vector code)
 * @author Stuart Inglis (stuart@reeltwo.com) (sparse vector code)
 * @version $Revision$
 */
public class PolyKernel extends CachedKernel {

    /** for serialization */
    static final long serialVersionUID = -321831645846363201L;

    /** Use lower-order terms? */
    protected boolean m_lowerOrder = false;

    /** The exponent for the polynomial kernel. */
    protected double m_exponent = 1.0;

    /**
     * default constructor - does nothing.
     */
    public PolyKernel() {
        super();
    }

    /**
     * Creates a new <code>PolyKernel</code> instance.
     * 
     * @param data       the training dataset used.
     * @param cacheSize  the size of the cache (a prime number)
     * @param exponent   the exponent to use
     * @param lowerOrder whether to use lower-order terms
     * @throws Exception if something goes wrong
     */
    public PolyKernel(Instances data, int cacheSize, double exponent, boolean lowerOrder) throws Exception {

        super();

        setCacheSize(cacheSize);
        setExponent(exponent);
        setUseLowerOrder(lowerOrder);

        buildKernel(data);
    }

    /**
     * Returns a string describing the kernel
     * 
     * @return a description suitable for displaying in the explorer/experimenter
     *         gui
     */
    @Override
    public String globalInfo() {
        return "The polynomial kernel : K(x, y) = <x, y>^p or K(x, y) = (<x, y>+1)^p";
    }

    /**
     * Returns an enumeration describing the available options.
     * 
     * @return an enumeration of all the available options.
     */
    @Override
    public Enumeration<Option> listOptions() {
        Vector<Option> result = new Vector<Option>();

        result.addElement(new Option("\tThe Exponent to use.\n" + "\t(default: 1.0)", "E", 1, "-E <num>"));

        result.addElement(new Option("\tUse lower-order terms.\n" + "\t(default: no)", "L", 0, "-L"));

        result.addAll(Collections.list(super.listOptions()));

        return result.elements();
    }

    /**
     * Parses a given list of options.
     * <p/>
     * 
     * <!-- options-start --> Valid options are:
     * <p/>
     * 
     * <pre>
     * -D
     *  Enables debugging output (if available) to be printed.
     *  (default: off)
     * </pre>
     *
     * <pre>
     * -C &lt;num&gt;
     *  The size of the cache (a prime number), 0 for full cache and 
     *  -1 to turn it off.
     *  (default: 250007)
     * </pre>
     * 
     * <pre>
     * -E &lt;num&gt;
     *  The Exponent to use.
     *  (default: 1.0)
     * </pre>
     * 
     * <pre>
     * -L
     *  Use lower-order terms.
     *  (default: no)
     * </pre>
     * 
     * <!-- options-end -->
     * 
     * @param options the list of options as an array of strings
     * @throws Exception if an option is not supported
     */
    @Override
    public void setOptions(String[] options) throws Exception {
        String tmpStr;

        tmpStr = Utils.getOption('E', options);
        if (tmpStr.length() != 0) {
            setExponent(Double.parseDouble(tmpStr));
        } else {
            setExponent(1.0);
        }

        setUseLowerOrder(Utils.getFlag('L', options));

        super.setOptions(options);
    }

    /**
     * Gets the current settings of the Kernel.
     * 
     * @return an array of strings suitable for passing to setOptions
     */
    @Override
    public String[] getOptions() {

        Vector<String> result = new Vector<String>();

        result.add("-E");
        result.add("" + getExponent());

        if (getUseLowerOrder()) {
            result.add("-L");
        }

        Collections.addAll(result, super.getOptions());

        return result.toArray(new String[result.size()]);
    }

    /**
     * 
     * @param id1   the index of instance 1
     * @param id2   the index of instance 2
     * @param inst1 the instance 1 object
     * @return the dot product
     * @throws Exception if something goes wrong
     */
    @Override
    protected double evaluate(int id1, int id2, Instance inst1) throws Exception {

        double result;
        if (id1 == id2) {
            result = dotProd(inst1, inst1);
        } else {
            result = dotProd(inst1, m_data.instance(id2));
        }
        // Use lower order terms?
        if (m_lowerOrder) {
            result += 1.0;
        }
        if (m_exponent != 1.0) {
            result = Math.pow(result, m_exponent);
        }
        return result;
    }

    /**
     * Returns the Capabilities of this kernel.
     * 
     * @return the capabilities of this object
     * @see Capabilities
     */
    @Override
    public Capabilities getCapabilities() {
        Capabilities result = super.getCapabilities();
        result.disableAll();

        result.enable(Capability.NUMERIC_ATTRIBUTES);
        result.enableAllClasses();
        result.enable(Capability.MISSING_CLASS_VALUES);
        result.enable(Capability.NO_CLASS);

        return result;
    }

    /**
     * Sets the exponent value.
     * 
     * @param value the exponent value
     */
    public void setExponent(double value) {
        m_exponent = value;
    }

    /**
     * Gets the exponent value.
     * 
     * @return the exponent value
     */
    public double getExponent() {
        return m_exponent;
    }

    /**
     * Returns the tip text for this property
     * 
     * @return tip text for this property suitable for displaying in the
     *         explorer/experimenter gui
     */
    public String exponentTipText() {
        return "The exponent value.";
    }

    /**
     * Sets whether to use lower-order terms.
     * 
     * @param value true if lower-order terms will be used
     */
    public void setUseLowerOrder(boolean value) {
        m_lowerOrder = value;
    }

    /**
     * Gets whether lower-order terms are used.
     * 
     * @return true if lower-order terms are used
     */
    public boolean getUseLowerOrder() {
        return m_lowerOrder;
    }

    /**
     * Returns the tip text for this property
     * 
     * @return tip text for this property suitable for displaying in the
     *         explorer/experimenter gui
     */
    public String useLowerOrderTipText() {
        return "Whether to use lower-order terms.";
    }

    /**
     * returns a string representation for the Kernel
     * 
     * @return a string representaiton of the kernel
     */
    @Override
    public String toString() {
        String result;

        if (getExponent() == 1.0) {
            if (getUseLowerOrder()) {
                result = "Linear Kernel with lower order: K(x,y) = <x,y> + 1";
            } else {
                result = "Linear Kernel: K(x,y) = <x,y>";
            }
        } else {
            if (getUseLowerOrder()) {
                result = "Poly Kernel with lower order: K(x,y) = (<x,y> + 1)^" + getExponent();
            } else {
                result = "Poly Kernel: K(x,y) = <x,y>^" + getExponent();
            }
        }

        return result;
    }

}
